1. Field of the Invention
The present invention relates generally to Power over Ethernet (PoE), and more particularly to a high speed interface for use in PoE systems.
2. Background Art
Ethernet communications provide high speed communications between data terminals.
Power over Ethernet (PoE) systems enable power transmission over the same transmission lines that carry data in an Ethernet link. Generally, power is generated at a Power Source Equipment (PSE) side of the PoE system and is carried over an Ethernet cable to a Powered Device (PD) side of the PoE system.
A PSE system generally includes a transceiver physical layer device (transceiver/PHY) having full duplex transmit and receive capability. The PSE system further includes a PSE controller that controls the DC voltage supply to the PD. A PD system also includes a transceiver/PHY device in addition to a PD controller, which performs a number of functions at the PD side, including monitoring the voltage and current at the PD side of the PoE system.
Typically, in a PSE or a PD, the electronics side (also called the isolated side) is electrically isolated from the wire side (i.e., the side where power is inserted at the PSE and where power is received at the PD). As such, in a PSE, the transceiver/PHY device is electrically isolated from the PSE controller. Similarly, in a PD, the transceiver/PHY device is isolated from the PD controller.
However, there is a need to cross the isolation barrier in order to communicate between the isolated side and the wire side both in a PSE and a PD system. For example, in a PSE system, the transceiver/PHY device needs to communicate with the PSE controller in order to turn on/off the power, read statistics, and receive information regarding PoE classes discovered by the PSE controller, for example.
Conventional systems use opto-isolators to cross the isolation barrier between the isolated side and the wire side. To minimize cost, however, only a few opto-isolators are used to implement a serial communications interface (e.g., 2-wire or 3-wire) between the isolated side and the wire side. The result is a slow interface mainly due to the limited bandwidth (typically on the order of 100 Khz) of opto-isolators.
The inefficiency of using opto-isolators is further accentuated in large, high end enterprise PoE systems with hundreds of PoE ports, for example, in which there is even more demand for real time communication and control between the isolated side and the wire side.
There is a need therefore for PoE systems having enhanced interface capabilities between the isolated side and the wire side both at the PSE and the PD, to enable enhanced PoE applications.